The present invention relates to a fluid delivering system using a non-self priming pressure pump, in which a pressure higher than atmospheric pressure is applied to the fluid on the intake side of the pump to eliminate gas cushions in the pump chamber. These pumps being used especially for supplying fluids to a pressure tank, e.g., to a carbonator for a post-mix beverage dispenser.
To lower investment costs and to achieve good efficiency when delivering fluids, pressure pumps of known construction are usually designed such that they satisfactorily meet requirements for operating only under normal operating conditions. The usual prerequisite for normal operating conditions is that fluid be present in the pressure-pump chamber. If, no fluid is available in the pressure pump chamber for delivery, a dry cycle will occur endangering the pumping systems to a high degree. Self priming, pumping systems are capable of correcting this condition if fluid is available on the intake side, but they are expensive to make and, also, their mode of operation is not particularly advantageous.
Therefore, for many fields of application, non-self-priming pressure pumps are the most expedient means for delivering fluids. However, care must be taken that this type pressure pump be continuously filled with fluid, particularly in the starting phase. Pressure pumps of this type are, for example, used for delivering water to a carbonator of a post-mix beverage dispenser in which refreshing drinks can be prepared from water enriched with CO.sub.2 and beverage concentrates. Fresh water supplied to such a carbonator is enriched with pressurized CO.sub.2 gas which is likewise supplied. If required, additional fresh water must be delivered to the carbonator against this pressure. As a rule, commercial water supply with the necessary delivery pressure is not available. For this reason, a pressure pump must be incorporated into the water supply line to advance water to the carbonator. Normally, replenishment of a carbonator with fresh water occurs discontinuously, i.e., only if there is a new demand for water due to the removal of carbonated water from the carbonator. It may come to pass that, due to unfavorable circumstances, a gas cushion develops in the chamber of the pump system. Pressure built up in the carbonator counteracts any fluid flow from the pressure pump, so that the gas cushion impeding the development of the pumping action cannot be removed by the pumping action. In order that the pressure pump can again operate properly and not be exposed to adverse effects due to dry cycles, it is necessary to vent the pump chambers, for example, manually.
A suitable signalling system and the presence of an attendant to detect the condition and to vent any gas cushions are necessary for this purpose. Depending on the design of the pump, a temperature switch or a temperature fuse can, in the event of overheating of the pump system, either turn the pump off during periods of overheating--which would lead to repeated dry cycles--or switch off the pump system permanently until an attendant becomes available again to repair the damage.